The role of prostaglandins in the control of renin secretion was examined in dogs maintained for one to two weeks on a diet containing 4 mEq Na ion/day. Infusion of indomethacin into the left renal artery (0.5 mg/kg followed by 388 microgram/min) caused significant increases in mean arterial blood pressure, and significant decreases in urine flow rate, renal blood, and renin secretion rate. Subsequent infusion of prostaglandin E2 (PGE2) at 4.12 microgram/min into the left renal artery caused significant increases in urine flow rate, renal blood flow, and renin secretion rate. The data suggests that PGE2 plays a role in the control of renin secretion.